A tour-de-force in polymer crosslinked aerogels

In the quest of building mechanically strong materials with low density and high porosity, polymer crosslinked aerogels stand as the most promising nano-engineered examples. Covalent attachment of polymers and bridging of skeletal nanoparticles of typical aerogels is demonstrated by using surface initiated polymerization (SIP) with a bidentate free-radical initiator structurally related to azobisisobutyronitrile (AIBN) and confined on mesoporous silica surfaces. Different monomers were introduced in the mesopores and upon heating at 70⁰C, all mesoporous surfaces throughout the entire skeletal framework were coated conformally with a 10-12 nm thick polymer layer indistinguishable spectroscopically from the respective commercial bulk materials. The new materials combine hydrophobicity with vastly improved mechanical properties. Resorcinol formaldehyde (RF) aerogels are pursued as precursors of carbon aerogels, which are electrically conducting. We have developed a HCl-catalyzed gelation process in CH₃CN, which is completed in ~ 2 h at room temperature as opposed to the week-long base-catalyzed literature process. The final aerogels are spectroscopically indistinguishable from typical base-catalyzed samples. Carbon (C-) aerogels are made by pyrolysis of RF aerogels, and combine electrical conductivity with a high open mesoporosity. Nevertheless, macropores facilitate mass-transfer and they could be beneficial for applications in separations or as fuel cell and battery electrodes. Here, we report a method where an open macroporosity is introduced by pyrolysing RF aerogels whose skeletal nanoparticles have been coated conformally and crosslinked chemically with an isocyanate-derived polymer. The new macroporous material was evaluated electrochemically for possible application as an electrode in batteries and fuel cells --Abstract, page iv